Channelized high-frequency signal receiving system



Nov. 15, 1949 F. MDM/ls CHANNELIZED H:IGH-FREQUENCYv SIGNAL RECEIVINGSYSTEMS Filed Nov. 21, 1945 mSSk uk@ zNVE/vrozz. FPA/wf /7 QQ ws BY 3and efciently received carrier frequencies over the range 108 to 118megacycles.

The amplified Waves from device 2 are applied to a mixer or frequencyconverter stage il which Y may take the form of any Well-known frequencyconverter tube such as conventionally used in the frequency conversionstage of a superheterodyne radio receiver. There is also applied to themixer 4 a local oscillator beat frequency which is generated by thelocal oscillator 5 which may be of any Well-known electron tube typehaving an adjustable frequency-determining or tuning element which isschematically illustrated b-y the arrow E. Oscillator 5 is of the typewhich is stabilized at its selected or tuned frequency by means of aparticular one of the series of piezo crystals l to I6. The frequenciesfrom oscillator 5 are multiplied in frequency by any Well-knownfrequency multiplier Il whereby the actual beat frequency applied tomixer 4 is ten times the frequency of the selected crystal. For example,crystal 'I may have a frequency of 9.5 megacycles and each of thesucceeding crystals may have a frequency which is 0.1 megacycle greaterthan the 4preceding crystal. The respective crystal frequencies areindicated in the drawing by the frequencies adjacent each of theirrespective conductors which are connected to corresponding stationarycontacts in the contact bank of a rotary switch I8. The rotatable brushI of this switch can therefore select any desired one of the crystalsfor connection to the oscillator 5.

As indicated by the dotted line connections, the tuning elements 3, 6,and the brush I9 are `ganged together to a common tuning indicator dial20 so that tuning of the amplifier 2 to any .desired frequency channelin the band 108 to 118 megacycles, automatically connects the proper.crystal in circuit and automatically tunes the -oscillator to thecorresponding channel fre- .quency In the drawing the numerals above therespective blocks, represent a particular selected spot frequency, Whilethe numerals below the respective blocks indicate the respectivefrequency bands. The gauging of the various elements 3, 5 and I9 is suchthat the resultant beat frequency in the output of mixer 4 is confinedto the band 13 to 13.9 megacycles, it being understood that the filter2l is of the band pass type to cover the 13 to 13.9 megacycle band. Thedevice 2| may be of any Well-known band pass type and may, if desired,include a corresponding band amplifier.

The signals from device 2! are then applied to another mixer orfrequency converter 22 Which in turn is supplied With a local beatfrequency from the local oscillator 23. Oscillator 23 is provided With atuning element 2li so that the oscillator can be tuned over the band 9.5to 10.4 megacycles as is the oscillator 5 already described. Theoscillator 23 is of the crystal stabilized type and is connected to therotary brush 25 of a switch whose stationary bank contacts are multipledto the respective crystals l to I0. The brush 25 and the tuning element2d are ganged through a suitable gearing or ratio coupling 25 to thedial 20 so that for each tenth of a turn of the dial 20 the brush 25makes a complete revolution, it being understood that the previouslydescribed brush i9 is ganged to the dial 29 so that brush I9 makes acomplete revolution for each complete revolution of dial 20. In otherWords, the received band of 108 to 118 megacycles may be considered asdivided into 100 separate frequency channels, each channel having aWidth of approximately 0.1 megacycle. When the tuning element 3 is tunedto any channel between 108 and 108.9 megacycles the brush I9 is inengagement with stationary contact 2. When the tuning element 3 is tunedto the band 109 to 109.9, brush I9 is advanced into engagement with thenext stationary Contact 28, and so on for the remaining frequencychannels. However the brush 25 is geared in a ten to one ratio to thebrush I9. Thus, When the element 3i is tuned to the 108 megacyclefrequency, brush 25 is in engagement with stationary contact 29. As thedevice 3 is tuned over the band 108 to 108.9 megacycles, the brush 25makes ten successive steps corresponding to each of the ten frequencychannels in the 108 to the 108.9 band. With this ganging arrangement,the beat frequency in the output of mixer 22 is1confined to a particularintermediate frequency, and in the system as illustrated thisintermediate frequency is 3.5 megacycles which is applied to acorresponding I. F. amplifier 30 whose output is applied to anyWell-known detector 3l for detecting the signal modulations in theamplified I. F. carrier. These signal modulations can then be applied toany Well-known audio frequency amplifier 32 whose output is connected toany suitable signal reproducer 33.

In the particular example illustrated in the drawing, it is assumed thatthe system is to receive on the channel 109.9 megacycles. Under theseconditions the dial 20 is turned so that the element 3 tunes theamplifier 2 to 109.9 megacycles. Since this desired channel is in thesecond decade, the turning of dial 20 automatically advances the brushI9 to the second stationary contact 28 thereby connecting crystal B incircuit and causing a local beat frequency of 96 megacycles to beapplied to mixer il. The difference frequency of 13.9 megacycles is thenamplified in the band pass amplifier 2l and is applied to the mixer 22.At the same time since the desired channel is in the ninth subdivisionof the second decade frequency range, the adjustment of dial 2i? asabove described causes brush 25 to be advanced to the ninth stationarycontact 34, thus connecting the 10.4 megacycle crystal I6 in circuitwith oscillator 23. There is thus producedr an intermediate beatfrequency of 3.5 megacycles Which is suitably amplified in the amplifier39.

If desired, the brush 25 and the tuning element '2li of oscillator 23can be independently adjusted so that they are not ganged to the dial26. Under that condition there would be provided two tuning knobs ordials, namely the dial 20 and another dial which controls the brush 25and the oscillator tuning element 24. The dial 2B would then becalibrated in one megacycle steps, and the dial for oscillator 23 Wouldbe calibrated in ten steps from 0.1 megacycle to 0.9 megacycle.

While one particular frequency conversion system and While oneparticular band of frequency channels have been described, it will beunderstood that changes and modifications may be made therein withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. A radio receiving system of the type adapted to receive on aplurality of selectable input carrier frequencies the frequencies beingdivisible into X groups and with Y frequencies in each group, aplurality of successive frequency converter stages of thesuperheterodyne type for the received carrier frequencies, meansselectively to vsupplyfthe `succeeding `stage 'with-any desired one of Ybeating oscillations of differentfreqnencies from those supplied to 4theiirst stage, a bank of piezo crystals the number of Acrystals beingequal to XLand each crystal Lbeing capable of simulv`taneouslyfstabilizing the Ilocal 'beating oscilla- "tionsf'of both said stages, alplurality of switches reach switchhaving asset lof bank contacts ,and-a selectively movable brush, said crystalsbeing connected in multipleto the bank contacts of each switch, and said brushes being individuallyconnected to the corresponding local oscillator generator for each ofsaid stages, to enable a single crystal to simultaneously stabilize bothsaid stages and to enable any desired combination of crystals to beconnected to said stages to simultaneously stabilize their respectivefrequencies.

2. A radio receiver of the double superheterodyne type to receive on anyone of a plurality of selectable input frequencies and comprising a pairof successive frequency conversion stages, means including an oscillatorgenerator to supply one stage with local beating oscillations, meansincluding another oscillator generator to supply the preceding stagewith local beating oscillations whose frequencies are multiples of thefirst-mentioned beating oscillations, a plurality of piezo crystals,each crystal being connectable simultaneously to both said generators tostabilize their respective frequencies, a multi-point switch forconnecting a selected one of said crystals to the first-mentionedoscillator generator, another multi-point switch for connecting saidselected crystal or any other one of said crystals to thesecond-mentioned oscillator generator and thereby maintaining theconverted frequency from said one stage uniform, regardless of thefrequency to which the receiver is tuned.

3. A radio receiver according to claim 2 in which each of said switchesincludes a set of fixed contacts one for each crystal, the fixedcontacts in both switches being connected in multiple to said crystalsfor connecting them in different combinations to said oscillatorgenerators.

4. A radio receiving system of the type adapted to receive a pluralityof selectable input carrier frequencies, a plurality of successivefrequency converter stages of the superheterodyne type for the receivedcarrier frequencies, means including an oscillator-generator to supplyone stage with local beating oscillations, means including anotheroscillator-generator to supply a succeeding stage with local beatingoscillations of a frequency different from the first-mentioned beatingoscillations, means to tune each oscillator to a plurality of beatingfrequencies, a single bank of piezoelectric crystals common to both saidoscillators, and switching means for connecting any one of said crystalsto both oscillators to control both oscillators simultaneously, and alsofor connecting said crystals in different combinations respectively tosaid oscillators and thereby to maintain the converted frequency of saidsucceeding stage constant, for any one of said selected inputfrequencies.

5. A radio receiver of the double superheterodyne type having an inputradio frequency i crystal-.controlled.tunable oscillator which-is con-`vnected to said-first converterthroughaifrequency multiplier, va.second frequency converter which is z-ccnnected to the output of said:first-converter to produce a'finaliintermediate frequency, a secf-ondsource oflocal beating oscillations for :said second converter .andincluding another :tunable crystal-controlled oscillator which isconnectedito 'said V,second converter, a vsingle .bank of piezocrystalsfor controlling both said local ,oscillators `a nrst-multi-pointswitchfor selectively connectfing Cany4 one `of said I.crystals to thefirstimentioned local oscillator, and a second multi-pointfswtchforvconnecting anyzone of said crystals to the second local oscillatorand thereby to maintain the intermediate frequency from said secondconverter constant, over the entire tuning range of said amplifier.

6. A radio receiver, comprising a tunable input radio frequencyamplifier, a first frequency converter connected to the output of saidamplifier, a band-pass filter connected to the output of said converterfor selecting one side band of the converted frequencies, a secondfrequency -converter connected to the output of said filter to producean intermediate frequency, an amplifier and detector for saidintermediate frequency; a rst local beating oscillator for said firstconverter and having a tuning element for tuning the said rst oscillatorover a predetermined frequency range of frequencies, another localbeating oscillator for said second converter having a tuning device fortuning said second oscillator over the same frequency range as the rstoscillator, a frequency multiplier connected between the first localoscillator and the rst converter, a bank of piezoelectric crystalscommon to both said oscillators each crystal being allotted to acorresponding one of the carrier frequency channels to be received andcovering the same frequency range as said oscillators, a multi-pointswitch having a movable contact arm and stationary contacts eachconnected to a respective crystal for selectively connecting any one ofsaid crystals to the rst local oscillator, another multi-point switchhaving a movable contact arm and stationary contacts each connected to arespective crystal for selectively and simultaneously connecting saidselected crystal or any other one of said crystals to the second localoscillator, and means connecting the movable contact arm of the firstswitch to the tuning element of said rst oscillator and to the tuningelement of said radio frequency amplifier to tune said amplifier to anydesired frequency channel and also for automatically connecting theproper crystal in circuit with the first local oscillator and ktherebymaintaining the frequency from said intermediate frequency constant, forevery carrier frequency channel to be received.

'7. A radio receiver of the double superheterodyne type, comprising aninput radio frequency amplifier tunable to group and unit frequencies, afirst frequency converter connected to the output of said amplifier, asecond frequency converter connected to the output of said firstconverter to produce a final intermediate frequency, a rst local beatingoscillator for the first converter, a second local beating oscillatorfor the second converter, each of said oscillators havingfrequency-adjusting means for maintaining said intermediate frequencyconstant over the entire tuning range of said amplifier, means tomultiply the frequency of the oscillations from the first localoscillator before applying them to the rst converter, each of said localoscillators 'being of the piezo crystal-controlled type, a bank ofpiezoelectric crystals connectable to said oscillators for controllingtheir respective frequencies, the number of crystals in the bank beingequal in number to the number of group frequencies to which the saidradio frequency amplifier can be tuned, and a pair of multi-pointswitches one for each of said oscillators for connecting said crystalsin different combinations respectively to said oscillators to maintainsaid intermediate frequency uniform, over the entire tuning range ofsaid amplifier.

FRANK M. DAVIS.

8 REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,753,444 Ohl Apr. 8, 19301,753,445 Ohl Apr. 8, 1930 2,235,768 Lock Mar. 18, 1941 10 2,354,148shaw July 1a, 1944

